Thickness and process optimization of planetary magnetron sputtered FeMnRh spin valves.

Thickness dependence and process optimization of planetary magnetron sputtered FeMnRh-based spin valves (SV) have been investigated in terms of the interrelationship between process conditions, microstructure, and magnetic properties. For the Cu spacer layer, sputtering at low power (0.5–1 kW) and low pressure (1–3 mT) give lower film resistivity. The ΔR/R reaches >9.0% for Cu thickness range of 18–22 Å and drops as Cu thickness increases in spin valves of structure: Ta50/NiFe50/CoFe20/Cu(t)/CoFe22/FeMnRh80/Ta50 Å. From the pinned layer thickness (CoFe) dependence of H[sub ex], an interfacial anisotropy energy (J[sub k]=H[sub ex]M[sub s]t) is calculated to be 0.14 erg/cm2 which is larger than the value reported for FeMnRh previously. Both H[sub ex] (400–480 Oe) and ΔR/R (7.3%–8.5%) were found to increase with FeMnRh sputtering pressure (3–15 mT) for Ta50/NiFe50/CoFe20/Cu26/CoFe22/FeMnRh110/Ta50 Å films. Two-step depositions (low and high sputtering pressure) of FeMnRh layer suggest that the higher H[sub ex] is mainly attributed to the interfacial smoothness at the CoFe/FeMnRh interface rather than the effect of smaller grain size of FeMnRh layer. The blocking temperature (T[sub b]) of these spin valves increases from 160 to 175 °C with increasing FeMnRh thickness from 80 up to 110 Å, after which it decreases to 170 °C at 120 Å. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]